1. Field of the Invention
This invention relates to a torque releasing clutch for a screw driver blade, particularly to one installed in a connect rod to be combined with a screw driver, permitting torque releasing steel balls to timely release the screw driver blade so that the connect rod may rotate idle not to turn the screw driver blade even if the screw driver still have some torque remained. In this way, the remaining torque of a screw driver may not harm and shock the blade slot of a screw, in addition to avoiding feeding back of the remaining torque to a user of the screw driver to cause harm to the user.
2. Description of the Prior Art
A known screw driver blade holder disclosed in a U.S. Pat. Nos. 4,284,923 and 4,753,142 includes a connect rod 1, and a combining rod 10 for connecting with an electric tool or a manual tool, and an E-shaped groove 11 for an E-shaped locking washer 110 to fit therein, and a fitting edge 12 for reversing rotation, an inner ring 15 and an outer ring 16 for the screw driver blade to be kept in an extended condition as shown in FIG. 3, for screwing off a screw deeply driven in an object. Further, the screw driver blade holder is provided with plural torque releasing ball holes 13 for releasing steel balls 130 fitted therein, and a combining groove 14 and an elastic locking ring groove 140 formed in an inner wall of the combining groove 14 for fitting an elastic locking ring 141 therein to fit in an annular recess 170 of the screw driver blade 17. The outer sleeve 15 has a central through hole 150 for the connect rod 1 to fit in, and a spring 151 fitted around the connect rod 1. Further an inner sleeve 16 is provided, to fit in the outer sleeve 15, with its inner end pushing one end of the spring 151 and having an annular recess 160 for the releasing steel balls 130 to fit in so as to timely releasing the driving torque of the screw driver blade.
When a screw is driven in an object with the screw driver blade in the condition shown in FIG. 1, the driver blade cannot be adjusted in its extended length to suit to the depth of the screws to be driven in an object. So the conventional screw driver blade cannot suit to various depths of screws to be driven in objects, and a screw such as a square screw has to leave a comparative long head on an object, hardly able to be driven with a good effect. Moreover, the driver blade 17 is fixed in the connect hole 14 of the connect rod 1 by means of the elastic locking ring 141, but the driver blade 17 is difficult to be taken off, needing a spanner to cause inconvenience.
Next, FIGS. 44 and 5 show a second conventional screw driver blade holder disclosed in a Taiwan patent No, M247354, which is provided with a spring 80 in a connect rod 8 for pushing a screw driver blade 81 forward, but the blade hole 82 for the driver blade is shaped hexagonal the same as the driver blade, having driving force, but no function of clutching action for releasing torque of the tool.
The first and the second conventional clutch for a screw driver blade have the common flaw that the screw driver blade is separated from the blade slot of a screw before the driver blade is not completely stopped turning after the screw is driven to a preset depth, with the hand of a user released from the switch of the tool. Then the driver blade has some remaining torque coming from the motor of the tool, continuing to turn to damage the blade slot of the screw and possibly hurting a user as well. Especially it happens often that a worker is working on a roof fixing metal plates, and for attempting to finish the work quickly, the worker may at once pull off an electric tool when a screw has been driven to a needed depth, preparing to move the body to a next location where another screw is to be fixed. At that time the worker may not stand in a most balanced condition as to fall down from the roof by the remaining torque of the electric tool.